Cancers in which mutations have been identified in putative tumor suppressor genes, such as the TP53 gene, the retinoblastoma (RBI) gene, the adenomatous polyposis coli (APC) gene, and the Wilms tumor (WTI) gene, frequently show loss of the corresponding allele on the homologous chromosome. To identify locations of tumor suppressor genes involved in uterine cancer, we examined loss of heterozygosity (LOH) by using genomic probes detecting RFLPs in 35 uterine cancers at 29 loci throughout the genome, and with highly informative microsatellite markers in 21 uterine cancers at nine putative or known tumor suppressor gene loci. High frequencies of allelic loss found at loci on 3p (71%), 9q (38%), 10q (35%), and 17p (35%) suggest that tumor suppressor genes involved in uterine carcinogenesis exist in these regions. There were no significant differences in frequencies of LOH between cancers of the uterine cervix and cancers of the uterine endometrium at any of the loci tested.